Passage of radiation through inhomogeneous, moving media. XIII. Causality, analyticity, group speed, transparency, and allied phenomena with emphasis on some recent calculations by Ko and Chuang

Journal Article · Thu Jun 15 04:00:00 EDT 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156220· OSTI ID:7051274

Lerche, I

A critical examination is made of some recent calculations by Ko and Chuang. They seek to show that original work by ourselves, and others, concerning the behavior of light propagating through differentially moving media is in error and that the fundamental structure of the results is, in fact, very different from the results we obtained: not excluding reversal of sign of some of the effects. We demonstrate that the results reported by Ko and Chuang are a consequence of two basic kinds of errors in their analysis. The first, and paramount, error is their use of fundamental basic kinds of errors in their analysis. The first, and paramount error is their use of fundamental relations in physics (such as the Kramers-Kronig dispersion relation) without due regard being given to the conditons imposed in arriving at the basic relationship in the first place, and thier use of particular relationships far outside their domains of validity as though they still held true.The second basic error is in a particular form of the refractive index, n, that Ko and Chuang use to illustrate their general points (which already suffer from the first basic error). The particular refractive index they use has the following unsatisfactory features: (i) it contains unstable modes in the upper half complex frequency plane: contrary to the conventional Kramers-Kronig relationship they invoke as a general principle; (ii) n/sup 2/<1 for all ..omega..: contrary to a specific of the Kramers-Kronig dispersion theory that Phi/sup infinity//sub 0/(n/sup 2/(..omega..)-1)d..omega..=0; (iii) the imaginary part of the dielectric positive (corresponding to absorption), yet the real part contains unstable modes, and the whole of the complex dielectric constant is nonanalytic in the upper half complex frequency plane; (iv) the form of n given by Ko and Chuang is purported to represent a warm, isotropic, Maxwellian plasma which is well known to be absolutely stable, so that no unstable modes can exist.

• Research Organization: Enrico Fermi Institute and Department of Physics, University of Chicago
• OSTI ID: 7051274
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 222:3; ISSN ASJOA
• Country of Publication: United States
• Language: English

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